It is the objective of this project: 1) To map the chromosomal site of integration of SV40 in different SV40 transformed human cell lines, 2) to establish the role of the SV40 A gene product in the proliferation of somatic cell hybrids between mouse peritoneal macrophages and SV40 transformed human cells, 3) to produce antisera for surface antigens coded by the human chromosomes carrying the SV40 genome, 4) to study the expression of SV40 T antigen in hybrids between mouse teratocarcinoma and SV40 transformed human cells, 5) to map the chromosomal site of integration of SV40 in different SV40 transformed mouse cell lines, 6) to map the transforming gene(s) of adenovirus 5 in adenovirus transformed cell lines, 7) to establish whether the genome of Epstein-Barr virus is chromosomally integrated in Burkitt's lymphoma cells derived from different patients; 8) to map the chromosomal site of integration of the murine sarcoma virus (MSV) genome in different MSV transformed human cells, 9) to map the sarcoma specific DNA sequences of Moloney sarcoma virus and of Kirsten and Harvey sarcoma virus in normal mouse and rat cells respectively, 10) to map the structural genes for endogenous RNA tumor viruses in different mouse strains, and 11) to study the expression of malignancy in somatic cell hybrids between virus transformed and normal human cells.